Tinnitus is described as a ringing or similar sensation of sound in the ears. It is a conscious expression of a sound that originates in an involuntary manner in the head of a person, or appears to do so. It is often associated with other hearing difficulties, but may present alone.
Tinnitus is classified into two types known as objective tinnitus and subjective tinnitus. Objective tinnitus is a rarer form and consists of head noises audible to people other than the sufferer. The sounds are generally external to the auditory system and many be caused by repetitive muscle contractions or inner ear structural defects.
The more common subjective tinnitus is much less understood. Sounds heard by sufferers can range from a metallic ringing, buzzing, popping or non-rhythmic beating sounds. The origins of this kind of tinnitus are as yet unclear. This is quite a distressing condition and prevents some sufferers from leading a fulfilling life. Antidepressants are commonly used to alleviate the distress felt because of the condition but do not stop the tinnitus. Various treatments have been tried to alleviate or cure tinnitus and have either been unsuccessful or have unproven results. Medications have proven unsuccessful.
A common treatment involves the use of tinnitus maskers together with counselling. Masking is the phenomenon whereby tinnitus is not perceived while another sound is presented to the sufferer's ear. Thus, the masking sound replaces the tinnitus sound. The masking sound is generally white noise, usually intermingled sine waves between 400 Hz and 10,000 Hz having a substantially flat frequency spectrum (that is many frequencies are present each to a substantially equal extent). Masking has also been attempted using music.
Hearing aids which increase normal speech above the level of the tinnitus may assist with a sufferer's hearing, however, these do not remove the tinnitus. In addition to assisting with hearing, the aids can introduce white noise to the ear(s) of the sufferer, thereby providing some masking.
Tinnitus retraining therapy is another treatment method which uses low volume white noise generators over a prolonged period of time in attempting to produce a less stressful response to the tinnitus. This approach is as yet unproven.
Alternative therapies used by some practitioners include prescribing herbal medications such as Gingko Biloba; and the use of acupuncture; hypnosis; electrical stimulation and bio-feedback. None of these treatments have shown any lasting effects.
To date, there has been no therapeutically successful treatment of tinnitus in terms of producing medium or long term remission.
It has previously been observed in tinnitus patients that there can be a brief period when tinnitus is absent or reduced after a masking signal ceases. This absence or reduction of tinnitus is called residual inhibition.
Residual inhibition usually lasts only a few seconds at the most. Because it is so short lived, it has previously been disregarded as being therapeutically useful. Attention to residual inhibition is actively avoided in current masking therapy.
Cochlear Implants (CI) have been noted to reduce tinnitus in some sufferers. The tinnitus is reduced while the cochlear implant is switched on and this constitutes masking. Residual inhibition has not been regularly demonstrated in sufferers having cochlear implants. Some sufferers have developed tinnitus for the first time after the cochlear implant has been implanted. Utilising a cochlear implant is not a recommended treatment for tinnitus
One worker in the field (Zeng Fan-Gang) is reported to have implanted a cochlear implant in one ear of a patient with normal hearing but severe suicidal tendencies induced by the symptoms of tinnitus. Cochlear implants generally destroy the normal hearing of the patient's implanted ear. The cochlear implant was used to provide masking. Low frequency modified sine waves were applied to the cochlear implant. There was some initial alleviation of the patient's symptoms, however, the patient did not experience residual inhibition and subsequently suffered from tinnitus rebound. So the presumed loss of hearing in one ear did not improve the patient's symptoms over time.
Residual inhibition can be described as complete, partial or rebound. In complete residual inhibition the tinnitus is totally absent after the cessation of the masking sound. In partial residual inhibition the tinnitus is reduced in intensity but still present after the cessation of the masking sound. In rebound residual inhibition the tinnitus can be louder after the cessation of the masking sound. It is common for initial complete residual inhibition to give way to subsequent partial residual inhibition if the tinnitus gradually returns.
In fact, residual inhibition is not sought or utilised as part of current tinnitus masking therapies. Jack Vernon, a founding father of masking therapy, states in his book Tinnitus diagnosis/treatment (Abraham Shulman publisher) at page 62: “Often, tinnitus patients tell us they cannot see the point of masking: “Why trade one sound for another?” Then we demonstrate masking, and often the patient immediately understands how it alone can produce relief. In the first place, a band of noise is aesthetically more acceptable than a high-pitched shrill tone. Second, outside sound can be ignored more easily than can the tinnitus. Despite this, however, many patients are overly impressed with the demonstration of residual inhibition. For some it represents the first time since its inception that they have not heard their tinnitus. Regardless of its temporary nature, they still expect a permanent residual inhibition to develop. We explain that masking is successful when it alone is the relief and that residual inhibition is not the goal of masking. Despite all these disclaimers, we have encountered clinicians who have recommended no masking because the patient did not display residual inhibition in the clinical test. We have also seen patients who would not continue the use of masking simply because they obtained no residual inhibition. In either of these situations, improper information and expectations have been conveyed” (emphasis added).
The inventor has treated tinnitus sufferers in his private clinic as an otologist for over 30 years.